GEO600 Detector Status
Harald LückMax-Planck Institut für Gravitationsphysik
Institut für Atom- und Molekülphysik, Uni Hannover
Worldwide Interferometer Network
Laser
Optical Layout
Michelson Interferometer
Output Mode Cleaner
Mode Cleaners
600m 10 W 5 W
1 W
~ 5 kW
10 kW atBeam Splitter
~50mW
Light power (specs)
GEO 600 Sensitivity specs.
GEO 600 Sensitivity specs.
Laser
Light Power (current)
Michelson Interferometer
Output Mode Cleaner
Mode Cleaners
10W 1W
300W atBeam Splitter
2W
~10mWMode Cleaners:
Troughput 80% 72%
Finesse 2700 1900
Visibility 96% 92%
98.65%
Power Recycling Cavity:
Mode matching 97%Finesse 450Linewidth 270 Hz
Optical Layout
Main Interferometer
Mode Cleaner
Laser Bench
Output Bench
Slave
Master
Master
Slave
entrance to vacuum system
Laser SystemMaster Laser:
Nd:YAG NPRO (non-planar ring
oscillator) 800mW @ 1064 nm
Slave Laser:
Nd:YAG injection-locked ring
cavity 14 W @ 1064nm less than 5% in higher
modes
Additional Information:
Talk:Wednesday 12:40 – 13:10 hBenno Willke
Poster session:
Tuesday 20:30 – 22:00 h
GEO Triple Pendulum Suspension
Thermal Noise Issues Monolithic Suspension
Silicate (Hydroxy- Catalysis) Bonding
Weld
Length and Frequency Control
MichelsonInterferometer
Output Mode Cleaner
Laser
Mode Cleaners25 MHz13 MHz37 MHz
Laser Frequency Stabilisation:
no rigid reference cavity
laser is directly stabilised to suspended cavities
3 sequential Pound- Drever-Hall control loops
common mode of the Power-Recycled Michelson
serves as frequency reference
Mode Cleaners
Output Mode Cleaner
Michelson Length Control
MichelsonInterferometer
Laser
15 MHz
10 MHz
Differential arm length:(gravitational wave signal)
heterodyne detection Schnupp modulation
Signal-Recycling control:
separate modulation frequency
reflected beam from beam splitter AR coating
Reaction Pendulum:
3 coil-magnet actuators at intermediate mass
Electrostatic actuation on test mass bias 500V, range 0-800V=4µm
Test Mass Actuators
<10Hz
>10Hz
Alignment Control
differential wave-front sensing
spot position control
4 degrees of freedom at MC 1
+4 at MC 2+4 at MI (common mode)+2 at MI (differential mode)+2 at Signal-Recycling cavity
16 + 20 = 36
Alignment Control
Magnet/coil actuators on IM
UGF: ~10Hz
Diff. MI Fast Auto-Alignment
Output port
Reduces misalignment below 50 nrad rms
Reliable locking over long timescales. Duty cycle >95%
Output mode
Radii Of Curvature of folding mirrors do not match
East ROC: 687m
North ROC: 666m
Spec: 640m
Thermal adjustment of ROC
+-
Thermal adjustment of ROC (II)
15 W10 W
15 W20 W
15 W30 W
15 W40 W
15 W50 W
15 W50 W
15 W60 W
15 W70 W
Signal Recycling
• Mirror Reflectivity = 99%
• Coil/magnet actuation directly to mirror
• Triple pendulum suspension with reaction pendulum chain
• Tunable between 550Hz and 5kHz
• Mode-healing
2x
Signal Recycling
• Mirror Reflectivity = 99%
• Coil/magnet actuation directly to mirror
• Triple pendulum suspension with reaction pendulum chain
• Tunable between 550Hz and 5kHz
• Mode-healing
5 kHz 3 kHz 1 kHz
Sensitivity Development
Dec. 2001
Aug. 2002
Nov. 2003
Jan. 2004
78%
98.5%
95.2%
98.7%